Since Hammerschmidt discovered in 1934 that gas hydrates block gas pipelines, research for the prevention of hydrate formation and agglomeration has become an important matter. Gas hydrates can be easily formed during the transportation of oil and gas in pipelines when the appropriate conditions are present. Water content, low temperatures, and elevated pressure are required for the formation of gas hydrates. The formation of gas hydrates often results in lost oil production, pipeline damage, and safety hazards to field workers.
There are two approaches to prevent or slowdown the formation of gas hydrates, thermodynamic inhibitors and low dosage hydrate inhibitors (LDHIs). Thermodynamic inhibitors are substances that can reduce the temperature at which the hydrates form at a given pressure and water content. Methanol and ethylene glycol are among the most common thermodynamic inhibitors used in the oil industry. Although thermodynamic inhibitors are quite effective, they require large doses to achieve high concentration in the water phase. Thermodynamic inhibitors are regularly dosed at concentrations as high as 50% based on water content during oil and gas production. Therefore, there is a substantial cost associated with the transportation and storage of large quantities of these solvents. A more cost-effective alternative is the use of LDHIs, as they generally require less than a 2% dose based on water content to inhibit the nucleation or growth of gas hydrates. There are two general types of LDHI, kinetic hydrate inhibitors (KHIs) and anti-agglomerants (AAs/AA). KHIs work by delaying the growth of gas hydrate crystals as anti-nucleators. AAs allow the hydrates to form but then prevent them from agglomerating and accumulating into larger masses capable of causing plugs in oil and gas pipelines. An AA enables gas hydrates to form but in the shape of a fluid slurry dispersed in the liquid hydrocarbon phase. In general, the water cut should be below 50% because otherwise the slurry becomes too viscous to transport.
There is an ongoing need for new and effective methods of inhibiting the formation of hydrate agglomerates, particularly those that are capable of operating under higher water-cuts.